Proximal causes of genetic variation between and within populations of rauli (Nothofagus nervosa)

Abstract

Agr. 36(2):229-238. Random Amplifi ed Polymorphic DNA (RAPD) markers were used to assess the genetic diversity of 587 individuals, belonging to 22 populations of Nothofagus nervosa that were distributed through the Coastal (38°S to 41°S) and Andes Mountains in CentralSouthern Chile (36°S to 40°S). The objective of this study was to complement the genetic inferences previously determined by isozyme analysis, in order to obtain more accurate genetic diversity estimations. We scored 81.8% of the polymorphic loci of the samples tested. The average incidence of genetic polymorphism within populations was high, with values ranging between 33% and 63%. Analysis of molecular variance (AMOVA) showed most of the genetic variation was distributed within populations (87.6%), but F ST values (F ST = 0.124; p < 0.00001) indicated that there was also a signifi cant difference among populations. A discriminant analysis revealed three geographically defi ned groups and showed that 14 loci explained 87.2% of the genetic differentiation among N. nervosa populations. Watterson's neutrality test and Ohta's two-locus analysis of linkage disequilibrium (LD) both suggested that stochastic demographic and environmental factors can partially explain the loci variation observed in the RAPDs. The role of the last glaciations, as well as some conservation and breeding strategies, may have infl uenced current genetic variation and fragmentation in this species.

Population genetic structure, genetic diversity, and natural history of the South American species of Nothofagus subgenus Lophozonia (Nothofagaceae) inferred from nuclear microsatellite data

“…() found values of ISSR diversity in Australian N. moorei similar to those reported by Carrasco et al. (). However, N. moorei is an isolated species with a very narrow distribution.…”

“…In accordance with Nothofagus anemophilous pollination, genecological studies on N. obliqua (Donoso ) and N. alpina (Donoso ) and population genetics studies conducted using nuclear markers in N. alpina (Pineda ; Carrasco and Eaton ; Carrasco et al. ) show a north‐to‐south clinal pattern of variation produced by large‐scale pollen flow and a climatic cline between the northern and southern populations. This pollen flow also facilitates interbreeding among species, generating natural hybrids in specific environmental conditions (i.e., N. alpina × N. obliqua (Donoso et al.…”

“…Nothofagus alpina from Chile has lower RAPD diversity than other long‐lived forest species, a result attributed to intense exploitation and substitution during the last century (Carrasco et al. ). Taylor et al.…”

“…Thus, in this study we will compare results obtained here with studies using other biparentally inherited markers in N. alpina : allozymes (Pineda ; Carrasco and Eaton ) and RAPDs (Carrasco et al. ). Furthermore, our microsatellite data will also complement recent studies on N. obliqua (Azpilicueta et al.…”

“…; Marchelli and Gallo ; Carrasco et al. ) and indirectly by genetic studies in other tree species in the area (Allnutt et al. ; Premoli et al.…”